Designer 2 Workflow - Possibility to use Designer & Texteditor

i startet to try Sencha Touch and Designer 2 some Days ago.
So far, i don't really understand the workflow.

I have to create an app that don't really looks like a standard app. How can i extend the layout in Designer? Can i extend my Designer-Project by a custom CSS an own IconClasses?

Sometimes, when i use helper tools like Designer, i prefer to make changes directly in the code, rather than searching for the Place to do it in the tool (if it is possible). Can i use a text editor to make changes directly in the code?

Sorry for my bad English an if this Questions eventually are a bit stupid.
It's hard for me to learn this concept in a Language i don't really use very often.

Anyway, Designer is mean to be an IDE even if still lacks some features like custom CSS/theme. But you can craft an application with it then on your deploy environment have your own css/theme.

For example, I'm developing an application backed up by Glassfish (JEE 6) using eclipse so I deploy Designer's project to /WebContent folder. Instead of using the generated designer.html I created one called app.html which includes my own code (DataUtils.js, UIUtils.js and so) and there I can, if I wanted, include my own theme. I will work on a theme for the app but for now I'm focused in application's code. I dont use "lauch" in designer, instead I lauch manually my app directly in the browser pointing to app.htmt instead of designer.html.

About code editing: The idea behing Designer is to easy the UI design and generate 100% well writen code so editing generated code is out of question. If you were able to modify it Designer be unable to manipulate again or your code would be overriden next time code is generated.

I know that there are a lot of limitation like UX components, use 3r party components and so but the time saved because the Designer worth the effort to look for an alternatives that normally, with hand crafted applications, were very easy.

I'm referring to english. It's not so easy to search in forums, Google or following screencasts and tutorials when you're missing practice and specially vocabularies ...

Do i understand you correct:
I create my App in Designer. There i can see the unthemed Version in the Preview. At same time i can create an app.html (or index.html), my own entry-point to the app, next to the designer.html, where i create my own styling?

Definitely knowing english (read at least) is very helpfull because is lot more information about technical stuff in english than other language.What language you spoke?

About styling:
Sencha's frameworks (ExtJS and Touch) use sass/compass to create theming.
It seems very frightening at first but is not so hard. For example, to change whole base color of the theme you only need to setup a variable then builr your css file.